The present invention relates to an infra-red reflector, and to an infra-red illumination system incorporating such a reflector. More specifically, the invention relates to an infra-red reflector and illumination system for providing a generally uniform intensity of illumination over a chosen area.
Surveillance of buildings, car parks and other premises for security purposes is often achieved with closed circuit television (CCTV) systems. CCTV cameras are normally mounted 6 to 8 meters above the ground to provide surveillance over a chosen area.
During daylight hours, high quality images can be obtained for a near field of vision (5 to 10 meters) in addition to a far field of vision (100 to 150 meters). These high quality images are obtained using simple ambient sunlight as an illumination source.
However, surveillance during night time hours requires an independent illumination source. Typically, an infra-red light source is used as a conventional means of illumination. The chosen area of surveillance is usually illuminated with infra-red lamps mounted above ground or above floor level in the vicinity of the CCTV cameras.
Illumination provided by infra-red sources according to conventional methods has the drawback of rapidly decreasing intensity measured at a distance from the source. This reduction in intensity with distance results from a physical phenomena known as the inverse square law. Because the intensity of illumination is very much greater at a point in the near field, the intensity of illumination of the far field is very much less than that of the near field. As a result, it is very difficult, if not impossible, to achieve sufficiently uniform illumination of the area, with the consequence that adequate quality of images throughout all of the chosen area cannot be achieved.